Electric pump system

ABSTRACT

An electric pump system includes a pump, a motor, and a control circuit. The motor drives the pump. The control circuit controls operation of the motor. The control circuit includes a determination circuit, a generation circuit, and a drive circuit. The determination circuit determines the amount of fluid to be discharged from the pump. The generation circuit generates, based on a maximum rotational speed of the motor, a control profile that is used to control the number of revolutions of the motor. The maximum rotational speed of the motor is set according to the environment in which the pump is used. The control profile is used for the pump to discharge the amount of fluid determined by the determination circuit in the shortest time. The drive circuit drives the motor based on the control profile generated by the generation circuit.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2015-249628 filed on Dec. 22, 2015 including the specification, drawings and abstract, is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems that drive a pump, and more particularly to systems that drive an oil pump for use in automatic transmissions.

2. Description of the Related Art

Systems that hydraulically operate a device are conventionally known in the art. For example, Japanese Patent Application Publication No. 2000-27992 (JP 2000-27992 A) discloses a system that drives a pump for use in automatic transmissions of vehicles. Japanese Patent Application Publication No. 2002-310102 (JP 2002-310102 A) discloses a system that drives a pump for use in hydraulic shovels.

The system described in JP 2000-27992 A includes a first pump, a second pump, and a motor that simultaneously drives these pumps. The pressure of oil discharged from the first pump is regulated by a line pressure control valve. The discharged oil whose pressure has been regulated is supplied to a hydraulic drive unit of a primary pulley of a continuously variable transmission (CVT) through a shift control valve, or is supplied to a hydraulic drive unit of a secondary pulley of the CVT without flowing through the shift control valve. Oil discharged from the second pump is supplied to the pulleys, a belt, etc. of the CVT through an oil cooler. The flow rate of each hydraulic line varies depending on the driving conditions of a vehicle. The flow rate required for the first pump and the flow rate required for the second pump are calculated based on the speed ratio, the line pressure, the oil temperature, etc. at that time. The flow rate required for the first pump and the flow rate required for the second pump are compared with each other. The number of revolutions of the pumps is determined so that oil can be supplied at the larger flow rate.

The system described in JP 2002-310102 A includes a first cylinder, a first hydraulic circuit that drives the first cylinder, a first pump that supplies an oil pressure to the first hydraulic circuit, a second cylinder, a second hydraulic circuit that drives the second cylinder, a second pump that supplies an oil pressure to the second hydraulic circuit, and an electric motor that drives the first and second pumps. If one of operation bodies is operated, the number of revolutions of the electric motor is set based on an operation signal corresponding to the amount of operation of the operation body. If both of the two operation bodies are operated, the number of revolutions of the electric motor is set based on an operation signal corresponding to the amount of operation of the operation body operated by a larger amount.

In systems that hydraulically operate a device, a pump is sometimes required to discharge a required amount of fluid, as described in JP 2000-27992 A. As described in JP 2000-27992 A, the pump can discharge a required amount of fluid if driven at the number of revolutions determined according to the amount of fluid to be discharged. However, it is difficult to drive the pump in an appropriate state if only discharge of the required amount of fluid is considered.

SUMMARY OF THE INVENTION

It is one object of the present invention to drive a pump in an appropriate state.

An electric pump system according to one aspect of the present invention includes a pump, a motor, and a control circuit. The motor drives the pump. The control circuit controls operation of the motor. The control circuit includes a determination circuit, a generation circuit, and a drive circuit. The determination circuit determines an amount of fluid to be discharged from the pump.

The generation circuit generates, based on a maximum rotational speed of the motor, a control profile that is used to control a rotational speed of the motor. The maximum rotational speed of the motor is set according to an environment in which the pump is used. The control profile is used for the pump to discharge the amount of fluid determined by the determination circuit in a shortest time. The drive circuit drives the motor based on the control profile generated by the generation circuit.

An electric pump system according to an embodiment of the present invention can drive a pump in an appropriate state.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a block diagram showing the general configuration of an electric pump system according to an embodiment of the present invention;

FIG. 2 is an illustration showing an example of a control profile;

FIG. 3 is an illustration showing another example of the control profile; and

FIG. 4 is a block diagram showing the general configuration of an application of the electric pump system.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the figures, the same or corresponding circuits are denoted with the same reference characters and description thereof will not be repeated.

FIG. 1 is a block diagram showing the general configuration of an electric pump system 10 according to an embodiment of the present invention. For example, the electric pump system 10 is used to drive pulleys of a continuously variable transmission (CVT). Specifically, the electric pump system 10 is used to move hydraulic oil between a cylinder that drives a primary pulley and a cylinder that drives a secondary pulley. The electric pump system 10 includes a pump unit 12 and an upper electronic control unit (ECU) 14.

The pump unit 12 is provided separately from the upper ECU 14. The pump unit 12 is placed away from the upper ECU 14. The pump unit 12 is connected to the upper ECU 14 via wiring, so that the pump unit 12 can receive signals from the upper ECU 14. The pump unit 12 can thus operate based on commands from the upper ECU 14.

The pump unit 12 includes a pump 16, a motor 18, and a controller 20. The pump 16, the motor 18, and the controller 20 will be described below.

The pump 16 sucks hydraulic oil through its suction port and discharges the sucked hydraulic oil through its discharge port. For example, the pump 16 is a positive-displacement rotary pump. In the positive-displacement rotary pump, the capacity of a chamber that accommodates hydraulic oil increases when the pump sucks hydraulic oil through its suction port, and the capacity of the chamber decreases when the pump discharges hydraulic oil through its discharge port. For example, the positive-displacement rotary pump may be a gear pump or a vane pump. For example, the gear pump may be an internal gear pump or an external gear pump.

The motor 18 drives the pump 16. For example, the motor 18 is a brushless motor.

The controller 20 controls operation of the motor 18. The controller 20 includes a drive circuit 201, a generation circuit 202, and a memory 203.

The drive circuit 201 drives the motor 18. The drive circuit 201 feedback-controls the motor 18. The drive circuit 201 includes a rotational speed control circuit 2011 and a current control circuit 2012. The rotational speed control circuit 2011 feedback-controls the rotational speed of the motor 18 so that an actual rotational speed (detected value) of the motor 18 follows a target rotational speed (command value). The current control circuit 2012 feedback-controls the drive current of the motor 18 so that an actual drive current (detected value) of the motor 18 follows a target drive current (command value). The period of feedback control of the drive current is shorter than that of feedback control of the rotational speed. Accordingly, when feedback control of the rotational speed is performed, an actual drive current (detected value) has already been controlled to a target drive current (command value).

The generation circuit 202 generates a control profile based on a signal that is sent from the upper ECU 14 (a signal indicating the amount of fluid to be discharged from the pump 16). The control profile is used when driving the motor 18. The control profile will be described in detail later.

The generation circuit 202 includes a conversion circuit 202A and a distribution circuit 202B. The conversion circuit 202A and the distribution circuit 202B will be described later.

The conversion circuit 202A sets the number of revolutions of the motor 18 which is required for the pump 16 to discharge the amount of fluid corresponding to a command from the upper ECU 14. That is, the conversion circuit 202A converts the amount of fluid to be discharged from the pump 16 to the total number of revolutions of the motor 18.

The amount of discharge per revolution of the pump 16 is considered when converting the amount of fluid to be discharged from the pump 16 to the number of revolutions of the motor 18. For example, the amount of discharge per revolution of the pump 16 is obtained in view of the temperature (oil temperature) of hydraulic oil that is discharged from the pump 16 and load characteristics of the pump 16. For example, the oil temperature is detected when converting the amount of fluid to be discharged from the pump 16 to the number of revolutions of the motor 18. The oil temperature is detected by, e.g., a temperature sensor. For example, the temperature sensor is placed in a conduit connected to the pump 16. The load characteristics of the pump 16 are determined by, e.g., the state of hydraulic oil in the conduit connected to the discharge port of the pump 16. The state of hydraulic oil in the conduit is determined by, e.g., the pressure of hydraulic oil (oil pressure) in the conduit. For example, the oil pressure is detected when converting the amount of fluid to be discharged from the pump 16 to the number of revolutions of the motor 18. The oil pressure is detected by, e.g., a pressure sensor. For example, the pressure sensor is placed in the conduit connected to the pump 16.

For example, a lookup table 401 is used when setting the amount of discharge per revolution of the pump 16. For example, the lookup table 401 shows the relationship among the oil temperature, the load characteristics of the pump 16, and the amount of discharge per revolution of the pump 16. The lookup table 401 is stored in advance in the memory 203.

For example, a lookup table 402 is used when setting the total number of revolutions of the motor 18. For example, the lookup table 402 shows the relationship between the amount of fluid to be discharged from the pump 16 (the amount of fluid corresponding to a command from the upper ECU 14) and the amount of discharge per revolution of the pump 16. The lookup table 402 is stored in advance in the memory 203.

The distribution circuit 202B distributes the number of revolutions of the motor 18 set by the conversion circuit 202A. The distribution circuit 202B distributes the number of revolutions of the motor 18 so as to minimize the time required for the pump 16 to discharge the amount of fluid corresponding to a command from the upper ECU 14. The control profile is generated by distributing the number of revolutions of the motor 18 by the distribution circuit 202B.

A control profile 30 will be described below with reference to FIG. 2. The control profile 30 shows the rotational speed of the motor 18 in every predetermined period T1. The control profile 30 includes a time period 301, a time period 302, and a time period 303.

The time period 301 starts when the motor 18 starts to be driven based on the control profile 30. That is, the time period 301 includes the starting point of the control profile 30. The motor 18 is not driven until the time period 301 starts. The rotational speed of the motor 18 is therefore zero before the time period 301 starts. In the time period 301, the number of revolutions of the motor 18 increases in every predetermined period T1. Namely, the rotational speed of the motor 18 (the rotational speed of the motor 18 in each period T1) increases in the time period 301. The rate (gradient) 3011 of increase in rotational speed of the motor 18 is constant in the time period 301. The motor 18 is rotating at its maximum rotational speed when the time period 301 ends.

The time period 302 starts when the time period 301 ends. Namely, the time period 302 is continuous with the time period 301. The rotational speed of the motor 18 at the end of the time period 301 is maintained in the time period 302. That is, the maximum rotational speed of the motor 18 is maintained in the time period 302. In the time period 302, the number of revolutions of the motor 18 therefore does not change in every period T1. The time period 302 is preferably equal to or longer than the time period 301.

The time period 303 starts when the time period 302 ends. Namely, the time period 303 is continuous with the time period 302. The time period 303 continues until driving of the motor 18 based on the control profile 30 is finished. That is, the time period 303 includes the end point of the control profile 30. The rotational speed of the motor 18 at the start of the time period 303 is the maximum rotational speed of the motor 18. The rotational speed of the motor 18 decreases in the time period 303. Namely, in the time period 303, the number of revolutions of the motor 18 decreases in every period T1. The rate (gradient) 3031 of decrease in rotational speed of the motor 18 is constant in the time period 303. The rotational speed of the motor 18 is zero after the time period 303 ends. Namely, the motor 18 is stopped when the time period 303 ends. The time period 303 is preferably shorter than the time period 302.

Referring back to FIG. 1, the distribution circuit 202B includes a rotational speed setting circuit 2021, a rate-of-increase setting circuit 2022, and a rate-of-decrease setting circuit 2023. The rotational speed setting circuit 2021, the rate-of-increase setting circuit 2022, and the rate-of-decrease setting circuit 2023 will be described below.

The rotational speed setting circuit 2021 sets the maximum rotational speed of the motor 18 (the rotational speed of the motor 18 in the time period 302) according to the environment in which the pump 16 is used. Specifically, the rotational speed setting circuit 2021 sets the maximum rotational speed of the motor 18 in view of, e.g., the temperature (oil temperature) of hydraulic oil that is discharged from the pump 16 and the load characteristics of the pump 16. A lookup table 403 is used when the rotational speed setting circuit 2021 sets the maximum rotational speed of the motor 18. The lookup table 403 is stored in advance in the memory 203. For example, the lookup table 403 shows the relationship among the oil temperature, the load characteristics of the pump 16, and the maximum rotational speed of the motor 18.

The rate-of-increase setting circuit 2022 sets the rate 3011 in the time period 301 (namely, the rate of increase in rotational speed of the motor 18 in the time period 301) according to the environment in which the pump 16 is used.

Specifically, the rate-of-increase setting circuit 2022 sets the rate 3011 in view of, e.g., the temperature (oil temperature) of hydraulic oil that is discharged from the pump 16 and the load characteristics of the pump 16. A lookup table 404 is used when the rate-of-increase setting circuit 2022 sets the rate 3011. The lookup table 404 is stored in advance in the memory 203. For example, the lookup table 404 shows the relationship among the oil temperature, the load characteristics of the pump 16, and the rate 3011.

The rate-of-decrease setting circuit 2023 sets the rate 3031 in the time period 303 (namely, the rate of decrease in rotational speed of the motor 18 in the time period 303) according to the environment in which the pump 16 is used. Specifically, the rate-of-decrease setting circuit 2023 sets the rate 3031 in view of, e.g., the temperature (oil temperature) of hydraulic oil that is discharged from the pump 16 and the load characteristics of the pump 16. A lookup table 405 is used when the rate-of-decrease setting circuit 2023 sets the rate 3031. The lookup table 405 is stored in advance in the memory 203. For example, the lookup table 405 shows the relationship among the oil temperature, the load characteristics of the pump 16, and the rate 3031.

For example, the upper ECU 14 controls a shift device of a vehicle. The upper ECU 14 includes a determination circuit 141. The determination circuit 141 determines the amount of fluid to be discharged from the pump 16. For example, the amount of fluid to be discharged from the pump 16 is the amount of fluid required to drive the pulleys of the CVT. The upper ECU 14 outputs the amount of fluid determined by the determination circuit 141 (the amount of fluid to be discharged from the pump 16) to the controller 20. Namely, a command that is output from the upper ECU 14 to the controller 20 indicates the amount of fluid to be discharged from the pump 16.

Operation of the electric pump system 10 will be described. First, the determination circuit 141 determines the amount of fluid to be discharged from the pump 16. Next, the upper ECU 14 transmits the amount of fluid determined by the determination circuit 141 to the controller 20. The generation circuit 202 generates the control profile 30 (see FIG. 2) based on the amount of fluid corresponding to a command from the upper ECU 14. Specifically, the conversion circuit 202A sets the number of revolutions of the motor 18 (the total number of revolutions of the motor 18) which is required for the pump 16 to discharge the amount of fluid corresponding to the command from the upper ECU 14. The distribution circuit 202B distributes the total number of revolutions of the motor 18 set by the conversion circuit 202A so as to minimize the time required for the pump 16 to discharge this amount of fluid. The control profile 30 is thus generated. The drive circuit 201 drives the motor 18 based on the control profile 30, whereby the pump 16 is driven. The amount of fluid corresponding to the command from the upper ECU 14 is thus discharged from the pump 16.

When generating the control profile 30, the electric pump system 10 refers to a maximum number of revolutions of the motor 18 so as to minimize the time required for the pump 16 to discharge the amount of fluid corresponding to the command from the upper ECU 14. Maximum capability of the motor 18 is thus obtained.

The control profile 30 has the time period 302. The maximum rotational speed of the motor 18 is maintained in the time period 302. Discharge efficiency of the pump 16 is thus improved.

The control profile 30 has the time periods 301, 303. The time required to increase the rotational speed of the motor 18 to the maximum rotational speed is minimized in the time period 301. The time required to stop the motor 18 is minimized in the time period 303. According to the control profile 30, the time period 302 during which the maximum rotational speed of the motor 18 is maintained can be increased. The discharge efficiency of the pump 16 can thus further be improved.

In the electric pump system 10, the generation circuit 202 is provided in the pump unit 12. This reduces the processing load on the upper ECU 14 as compared to the case where the upper ECU 14 generates the control profile.

In the electric pump system 10, the pump 16 is driven based on the control profile. The time required to discharge the amount of fluid corresponding to a command from the upper ECU 14 can thus be known before the pump 16 starts to be operated.

In the electric pump system 10, the time required to discharge the amount of fluid corresponding to a command from the upper ECU 14 can be designated by appropriately setting the lengths of the time periods 301, 302, 303, as long as it is within the capability of the pump 16.

The electric pump system according to the present embodiment includes a pump, a motor, and a control circuit. The motor drives the pump. The control circuit controls operation of the motor. The control circuit includes a determination circuit, a generation circuit, and a drive circuit. The determination circuit determines an amount of fluid to be discharged from the pump. The generation circuit generates, based on a maximum rotational speed of the motor, a control profile that is used to control a rotational speed of the motor. The maximum rotational speed of the motor is set according to an environment in which the pump is used. The control profile is used for the pump 16 to discharge the amount of fluid determined by the determination circuit in a shortest time. The drive circuit drives the motor based on the control profile generated by the generation circuit.

In the electric pump system, the generation circuit refers to the maximum rotational speed of the motor when generating the control profile. Accordingly, maximum capability of the motor can be obtained by driving the motor based on the control profile. That is, the electric pump system can drive the pump in an appropriate state.

For example, the environment in which the pump is used includes a condition that affects operation of the pump. For example, this condition includes the viscosity (temperature) of fluid that is discharged from the pump, the state of fluid (e.g., the pressure of the fluid) in a conduit connected to a discharge port of the pump. For example, this condition may be directly detected by a sensor or may be estimated from the detection result of the sensor.

The control profile preferably includes a first time period, a second time period, and a third time period. In the first time period, the rotational speed of the motor is increased from an initial rotational speed at the time the motor is driven based on the control profile to the maximum rotational speed at a maximum rate of increase that is set according to the environment in which the pump is used. In the second time period, the maximum rotational speed is maintained. In the third time period, the rotational speed of the motor is decreased from the maximum rotational speed to the initial rotational speed at a maximum rate of decrease that is set according to the environment in which the pump is used.

In this case, the time it takes for the rotational speed of the motor to increase from the initial rotational speed to the maximum rotational speed and the time it takes for the rotational speed of the motor to decrease from the maximum rotational speed to the initial rotational speed can be reduced. The time period (second time period) in which the maximum rotational speed is maintained can therefore be increased. Maximum capability of the motor can thus be obtained.

In the case where the control profile includes the first to third time periods, the generation circuit preferably includes a rotational speed setting circuit, a rate-of-increase setting circuit, and a rate-of-decrease setting circuit. The rotational speed setting circuit sets the maximum rotational speed according to the environment in which the pump is used. The rate-of-increase setting circuit sets the maximum rate of increase according to the environment in which the pump is used. The rate-of-decrease setting circuit sets the maximum rate of decrease according to the environment in which the pump is used.

In this case, the maximum rotational speed, the maximum rate of increase, and the maximum rate of decrease can be set appropriately.

In the electric pump system, a pump unit may include the pump, the motor, the generation circuit, and the drive circuit. In this case, the control profile can be generated in the pump unit. This can reduce the processing load on a control device as compared to the case where the control profile is generated by the control device provided separately from the pump unit.

In the electric pump system, a pump unit may include the pump, the motor, and the drive circuit. In this case, the determination circuit and the generation circuit are provided separately from the pump unit. This ensures flexibility in arranging the components of the electric pump system. Since the control profile is not generated in the pump unit, the processing load on the pump unit can be reduced.

Another embodiment will be described below. In the control profile, the rate of increase in rotational speed of the motor 18 need not be constant over the entire time period 301. For example, as shown in FIG. 3, the rate 3012 of increase in rotational speed of the motor 18 may be gently changed in the beginning and the end of the time period 301.

The rate of decrease in rotational speed of the motor 18 need not be constant over the entire time period 303. For example, as shown in FIG. 3, the rate 3032 of decrease in rotational speed of the motor 18 may be gently changed in the beginning and the end of the time period 303.

The control profile 30 need not necessarily be generated in the pump unit 12. For example, as shown in FIG. 4, the upper ECU 14 may include the generation circuit 202 that generates the control profile 30. 

What is claimed is:
 1. An electric pump system, comprising: a pump; a motor that drives the pump; and a control circuit that controls operation of the motor, wherein, the control circuit includes a determination circuit that determines an amount of fluid to be discharged from the pump, a generation circuit that generates, based on a maximum rotational speed of the motor which is set according to an environment in which the pump is used, a control profile of a rotational speed of the motor which is used for the pump to discharge the amount of fluid determined by the determination circuit in a shortest time, and a drive circuit that drives the motor based on the control profile generated by the generation circuit.
 2. The electric pump system according to claim 1, wherein, the control profile includes a first time period in which the rotational speed of the motor is increased from an initial rotational speed at the time the motor is driven based on the control profile to the maximum rotational speed at a maximum rate of increase that is set according to the environment in which the pump is used, a second time period in which the maximum rotational speed is maintained, and a third time period in which the rotational speed of the motor is decreased from the maximum rotational speed to the initial rotational speed at a maximum rate of decrease that is set according to the environment in which the pump is used.
 3. The electric pump system according to claim 2, wherein, the generation circuit includes a rotational speed setting circuit that sets the maximum rotational speed according to the environment in which the pump is used, a rate-of-increase setting circuit that sets the maximum rate of increase according to the environment in which the pump is used, and a rate-of-decrease setting circuit that sets the maximum rate of decrease according to the environment in which the pump is used.
 4. The electric pump system according to claim 1, wherein, a pump unit includes the pump, the motor, the generation circuit, and the drive circuit.
 5. The electric pump system according to claim 1, wherein, a pump unit includes the pump, the motor, and the drive circuit, and the determination circuit and the generation circuit are not included in the pump unit and are provided separately from the pump unit.
 6. The electric pump system according to claim 4, further comprising: an upper electronic control unit that sends a command to the pump unit.
 7. The electric pump system according to claim 6, wherein, the upper electronic control unit is placed away from the pump unit. 